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Regulatory Assets and Liabilities (Unamortized Defeance Costs and Standard Cost Recovery) (Details) $ in Millions, $ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2018 USD ($) | Dec. 31, 2018 CAD ($) | Dec. 31, 2017 CAD ($)
Nova Scotia Power Inc. [Member] | Defeased Debt [Member] |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |
Long-term Debt |  | $ 759 | $ 726
Grand Bahama Power Company Limited [Member] | Steam Plant [Member] |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |
Public Utilities, Property, Plant and Equipment, Amount of Loss (Recovery) on Plant Abandonment | $ 21 |  |

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